Electroplating of nickel



United States Patent 6 2,782,155 ELECTROPLATING F NICKEL Arthur H. Du Rose, Euclid, and John 1). Llttle, Bay Village, Ohio, assignors to The Harshaw Chemical Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Application February 16, 1954,

Serial No. 410,715 g 7 Claims. (Cl. 204-49) This invention relates to electrodeposition of nickel and more specifically to a process for producing electrodeposits of greatly increased. brightness and smothness, as taken from the plating solution, without bufiing or polishing of any sort.

This application is a continuation-in-part of our copending application, SerialN'o. 278,957, filed March 27 1952, and our copending application, Serial No. 338,560, filedFebruary 24, 1953, which was a continuation-in-part of application SerialNo. 278,958, filed March 27, 1952, all now abandoned.

This invention is, primarily concerned with the fact that although electrodeposits takentromacid. nickel plating solutions containing coumarin exhibit extraordinary smoothness they are only semi-bright, and attempts to increase their brightness by the use of addition agents of the type of saccharin or naphthalenesulfonic acids result in improved brightness with loss of smoothness when the surface being coated is quite smooth, and can result in decrease in both smoothness and brightness when the surfaceto be coated is quite rough: It was found, for example, that when an-aqueous, acid solution containing 240 grams per liter of nickel sulfate heptahydrate, 40 grams per liter of nickel chloride hexahydrate. and 40 grams per liter of boric acid was utilized and coumarin was used in concentration of 0.25 gram pertliter as the sole addition agent, a semi-bright deposit was obtained having a smoothness increase over the base metal of approximately 4 microinches where the base metal had a smoothness in the order of 6 to 10 microinc'hes, measurements having been made with the Brush surface analyzer. Such an increase in smoothness is remarkable, and this property of coumarin has formed the basis'of a commercial semi-bright solution now beiug'widely used. When the attempt was made to increase the brightness by the addition of agents such as saccharin or naphthalene sulfonic acids, it was found thatincreased brightness was secured, but at the cost of a part of the smoothing action of the coumarin. For example, it was found that when the above described solution was varied by adding 3.5 grams per liter of naphthalene disulfonic acid an increase in brightness was secured, but the gain in smoothness over the base metal was only about 2.2 microinches, the same type of base metal being used. If, instead of using naphthalene sulfonic acid-s, saccharin was used to improve the brightness, improved brightnesswas obtained and the gain in smoothness was about'the same. Many other sulfonic acids and sulfonamides; show similar results. When the surface to be coated is not so smooth, e: g. 20- to 29 R. M. S. as shown by the Brush: surface analyzer, the loss of the smoothing action maybe so great as to overshadow the tendency toward increased brightness and actually appear to decrease the luster of the deposit.

In accordance with the present invention it has now been discovered that a large portion of the lost smoothing action just described can be restored if there is added, in addition to the coumarin, not only an aromatic sulliterlof. nickel chloridehexahydrate, andtrom 1 0 to 50 grams per liter, preferably 15 to grams per liter, of.

, 2' fonamidmbutalso one or more of certain organic, level ingaddition agents or the following class: V Polyalkylene glycols, compoundsof the form mcnzcnioynn Where n is an integer from 10. to and a radical selected from the class consisting of "radicals in'the form RQ and RNH, where R is selected from the class consisting' of hydrogen, alkyl radicals having from 1 to 20 carbon atoms and aryl radicals having from 1 to 20 carbon atoms.

As' examples may be mentioned,

(a) Polyethylene glycohmolecular Wt; 500 (b) Polyethylene glycol, molecular wt. 1000 (c) PhO(CH2CHzO)'nH, n being an integer from 10 to 100 (d) PhNH(CH2OH2O)wH, n being an integer from 10 to 100 (2) Compounds like (0) and (d) wherein from 1 to 50% of the CHzCHzO groups are replaced by CHzCHzCl-lzo groups.

While these leveling agents. do not completely restore the full smoothing action of cour'nar'in, they do, in some instances, approach that result, and i'n'ot'her instances restore a large portion of it.

The preferred acid nickel solution in connection with which the invention may be realized is an aqueous solution containing nickel sulfate equivalent to from 100 t-o' 400' grams per liter of nickel sulfate heptahydrate, nickel chloride equivalent to from 10 to 75 grams per boric acid orother buffer such as formic acidor citric acid. To this fundamental solution there may be added. in accordance with the present-invention one or morearomatic sulfonamide's to a concentration from /2 gram per liter to saturation, one orii'no're coumar-in compounds to a concentration from 0.01 to 0.5 gram per liter, andoneor more leveling agents of the above indicated class in concentrations less than half a gram per liter, for example, from 0.0005 to 0.3 gramper liter. The concentrations of these compounds required for best results will be within the ranges indicated in the respective tables opposite each of said compounds, andvery desirably will be'approximately the specific concentration setforth opposite each compound in the tables.

The compounds listed in Table l are examples of sulfur compounds which when used in connection with coumarin and certain coumarinderivatives produce an increase in brightness with some loss in smoothness. Numerous other similar compounds producethe same effect invarying degree. They are aromatic sulfonamides and sulfimides. The compounds of Table II are examples of cournarin compounds which can be used. Alkyl and acyl derivatives of coumarin having 1 to 4 carbon atoms, and the chlorine and carboxy derivatives thereof are suitable. The compounds listed in Table III are examples of or ganic compounds eiiective to increase smoothing power (and brightness) of coumarin type smoothing agentsllos t by the addition of sulfur compunds of the type of those listed in Table I. C-our'n'arln sulfonic acids are not equivalent to the-above indicated cou'mari'n compo nds.

Preferably, the solutions are operated in pH range from 2.5- to 415, the temperature is maintained within the range from F. to F., and the cathode current density is maintained within the range from 5 to 100 A. S. F.

Formaldehyde may be used in the above described solutions at a concentration of from 0.05 to 0.5 gram per liter for the purpose of retarding or minimizing the efiect of breakdown products of coumarin or derivative such as listed in Table II.

Specific examples which have yielded excellent results are indicated in Table IV.

Other basic solutions capable of yielding nickel ions for electrodeposition may be employed. Preferably there should be present in the solution at least one nickel salt of the class consisting of nickel sulfate, nickel chloride, nickel fiuoborate and nickel sulfamate. The nickel ion concentration should in any case be within the range which would result from the presence of from 100 to 400 grams per liter of NiSO4.7H2O.

Table 1 Optimum Preferred Rang Concentrag./1. tion, g./l.

(1) Benzene suli'onemide (PhSOzNHz) 0. 5 to 3. 1.0 (2) p-Tolueue sullonamlde (011 0 114802- NHz) 0. to 3.0 1.0 (3) Saccharln (o-beuzosulfirnld) 0. 5 to 3.0 1.0 (4) Dlbenzene sull'onnmide (PhSOzNHSO Ph) and its mono-end-dichloro derivatives-. 0 5 to 5 0 0 (5) p-Benzene-bls (N-sulphonylbenzenesulfonemide (PhSOZNHSOZCQHISOINHSOT Ph) 0. 5 to 6.0 1.0 (6) N-ethane sullonyl benzene sulionamide... 0. 5 to 5.0 1.0 (7) Monoand di-chlorobenzene sulfenamides. 0. 5 to 5.0 1.0 (8) Monoand di-chloro derivatives of (2) and (5) above 0. 5 to 5.0 1.0 (0) Bi-dlbenzenesulionamide (PhSOzNHSOz- C5H4CeH4SOzNHSOgPh) 0 5 t0 5. 0 1. 0 (l0) Monoand dlchloro derivatives of (9) above 0. 5 to 5.0 1. 0 (11) Dlbenzeno sulionamide ether (PhSOz- NHsozcsH oCaHtSOzNHSOgPh) 0 5110 5. 0 1. 0

Table II Preferred Range, gJl. Concentration, gJl.

Coumarin. 0. 05 to 0. 0. 1 B-chloro coumarlm O. 05 to 0.25 0. 1 G-chloro coumarin. 0. 05 to 0. 25 0. 1 i-methyl eoumerin--- 0. 05 to 0.25 0. 1 G-csrboxy coumarin- 0. 05 to 0. 25 0. 1

Table III Preferred Range, g./l. Concentration, g./l.

(1) Polyethylene glycol (M. W 500) .001 to 05 .01 (2) Polyethylene glycol (M. W 1,000) .001 to .05 .01 (3) PhO(CH1CH O),J-I, n being an integer from 10 to 100 .001 to .05 .01 (4) PhNH (CH O),.lI, 11, being an integer from 10 to 100 .001 to .05 .01

Table IV Grams per Liter Nl O4.7H2O 300 300 300 NiClz.6H2O 45 45 45 H3 40 40 40 Sodium lauryl sulfate. 0. 06 0. 06 0.00 Coumarln 0. 1 0.1 0.1 Saccharln 0. 5 lbenzene sulfonamide 1.0 Bl-dlbenzene sulfonamide 1. 0 Polyethylene Glycol PhO (CH1CH20)10H .01 01 01 Having thus described the invention, what is claimed is: l. A solution for electrodeposition of nickel inthe form of bright and smooth deposits, said solution containing a nickel ion yielding compound of the class consisting of nickel sulfate, nickel chloride, nickel sulfamate and nickel fluoborate together with cooperating addition agents, one of said addition agents being an organic sulfur compound containing the group one thereof being selected from the class consisting of coumarin and its alkyl, acyl, chlorine and carboxy derivatives and a third thereof being a polyalkylene glycol compound of the formula R(CH2CH20)nH where n is an integer from 10 to 100 and R is a radical of the class consisting of RO and R'NH, R being selected from the class consisting of hydrogen, alkyl radicals having from 1 to 20 carbon atoms and aryl radicals having from 1 to 20 carbon atoms, said first mentioned addition agent being present in concentration from one-half gram per liter to saturation, said second mentioned addition agent being present in concentration from 0.01 to 0.5 gram per liter and said third mentioned addition agent being present in concentration from 0.0005 to 0.3 gram per liter.

2. A process for producing bright, smooth electrodeposits of nickel comprising electrolyzing between an anode and a cathode a solution containing nickel sulfate equivalent to from 100 to 400 grams per liter of nickel sulfate heptahydrate, nickel chloride equivalent to from 10 to 75 grams per liter of nickel chloride hexahydrate and a group of three cooperating addition agents, one of said addition agents being an organic sulfur compound containing the group coum-arin and its alkyl, acyl, chlorine and carboxy derivasaturation, said second mentioned addition agent being present in concentration from 0.01 to 0.5 gram per liter and said third mentioned addition agent being present in concentration from 0.0005 to 0.3 gram per liter.

3. A process according to claim 2 wherein said solution contains from 10 to grams per liter of boric acid.

4. The invention defined in claim 2 wherein said organic sulfur compound is saccharin.

5. The invention defined in claim 2 wherein said organic sulfur compound is bidibenzene sulfonamide.

6. The invention defined in claim 2 wherein said organic sulfur compound is dibenzene sulfonamide.

7. The invention as defined in claim 2 wherein said third mentioned addition agent is present in concentration from 0.001 to 0.05 gram per liter.

References Cited in the file of this patent UNITED STATES PATENTS Brown Oct. 3, 1950 Du Rose Apr. 14, 1953 

1. A SOLUTION FOR ELECTRODEPOSTION OF NICKEL IN THE FORM OF BRIGHT AND SMOOTH DEPOSITS, SAID SOLUTION CONTAINING NICKEL ION YIELDING COMPOUND OF THE CLASS CONSISTING OF NICKEL SULFATE, NICKEL CHLORIDE, NICKEL SULFAMATE AND NICKEL FLUOBORATE TOGETHER WITH COOPERATING ADDITION AGENTS, ONE OF SAID ADDITION AGENTS BEING AN ORGANIC SULFUR COMPOUND CONTAINING THE GROUP 